Subaru ECU Placement - Rear Passenger Tail Light Compartment

I've decided to re-position my Subaru ECU in the passenger tail light compartment that is opened up when the VW engine, relay and air snorkel are pulled out.  Here's a basic photo of the protective ECU box I'm installing and its location in the engine bay.

ECU box placement in rear passenger tail light compartment

Many people do not want to put their Subaru ECU in the engine bay, citing things like "the elements will ruin your ECU" or "VW engineers did not put ECUs in the engine bay and they know best".  Well, that was the 1980s and things change as technology and innovation advances.  Besides, if VW engineers know "best", why am I replacing their engine with a Subaru?  :)

Subaru/Vanagon conversion experts likeVanaru (Vanaru.com), Ben @ (benplace.com) and Paul Guzyk (BoulderHC.com), do every conversion this way and are quite successful at it.  I personally chose this location for many reasons:

1. The wiring harness ends up clean and straight forward - essentially, the wiring harness becomes a true plug-and-play, turn-key installation.  Initially, I went with a RMW harness (their default location for the ECU is in the rear bench seat), but this solution ends up being two harnesses, one for the main engine and another separate sub-harness for the ALT, voltage sensor, AC compressor, starter, fuel pump, and coolant level sensor.  After seeing the slick turn-key solution provided by Vanaru that easily combined all these into a single harness, I just had to redo it that way!
2. This single, wiring harness is visible 100% from the engine bay rather than having some portion of it tucked away behind the firewall.  I like being able to easily inspect my harness without getting under my van.
3. The wiring harness wraps around the back and top of the engine bay, staying out of the way of road hazards.  In contrast, when locating the ECU in the rear bench seat, the wiring harness is exposed to these hazards between the firewall and bench seat opening.
4. It utilizes the newly opened space in the engine bay that would be wasted otherwise.
5. It opens up room for storage in the rear bench seat or closet, which are two other common locations for Subaru ECUs.  That said, I'm a storage Nazi.  For instance, I'm also removing my rear heater to open up even more space under the rear bench seat. You may not care about storage like I do.
6. Diagnostic ports (OBD2 and the proprietary Subaru ones) are more easily reached right in the engine bay compared to the rear bench seat area.  So, a mechanic can more easily scan & reset codes from this location.

The photo here shows how I plan to layout the harness.  It is based on the Vanaru design.  It will be basically the same except where noted in RED.  I'll be tying in my ALT harness into the main harness a little differently.

Example Vanaru conversion that I'll be using as a prototype for my wire harness layout and ECU box placement

If you put your ECU in the engine bay, you need to protect it from the elements!  I describe how I am doing this with full step-by-step DIY "how to" here:  http://westycamper.blogspot.com/p/ecu-box.html